Rational defect and anion chemistries in Co3O4 for enhanced oxygen evolution reaction

Mesoporous Co3O3.87◻0.13 (◻ represents oxygen vacancies) and Co3O3.87F0.13 electrocatalysts, integrating advantages of oxygen vacancies and fluorine anion, were deployed. Co3O3.87◻0.13 and Co3O3.87F0.13 showed enhanced oxygen evolution reaction (OER) with overpotentials of 440 mV and 430 mV at 10 mA cm−2, Tafel slopes of 56 mV dec-1 and 56 mV dec-1, turnover frequency (TOFη= 400 mV) of 0.023 s-1 and 0.042 s-1 respectively, as compared to Co3O4 (520 mV, 64 mV dec-1, 0.0005 s-1) in the alkaline medium. Physicochemical characterizations showed that oxygen vacancies and the substituted fluorine modified the electronic structure, leading to the enhanced activity for OER process, consistent with the theoretical calculation. This approach provides ideas for rational design of new defective fluorinated oxide, with the feasible extension of such an approach to a wide variety of transition metal oxides. © 2020 Elsevier B.V.